The Inca built agricultural terraces in four circular depressions at the site of Moray. The largest depression has a diameter of 600 feet. (Roger Atwood)

Fields of waving quinoa and barley line the road on the way to Moray, an ancient Inca site a 90-minute drive from Cuzco, Peru. In the springtime, when I visited, the fields were erupting in a pastel galaxy of pink, purple, yellow, beige, and sky-blue, each color denoting the flower of a particular variety of pea, potato, or grain. The soil here is a rich mahogany red; the snow-capped Salcantay range seems to float in the distance.

When I arrived at the site, I left my car, walked a few feet, and suddenly found myself gazing into a 230-foot-deep abyss, one of the four enormous bowls lined with concentric stone terraces that are known collectively as Moray. It is a place that confounds everything one would expect to see in a site built by the Inca and it reminds us that despite decades of archaeological research, we really understand very little about them.

The Inca were fond of building settlements in precarious places--mountain saddles, ledges, valley walls --that made the most of their realm's sublime mountain vistas. The Inca Trail offers a four-day string of such sites, ending with the most glorious of all, Machu Picchu, and its 360-degree panoramic view that makes you feel like a condor in flight.

Moray, by contrast, is an inward journey. The largest bowl is some 600 feet in diameter and its sides are arranged in 12 orderly terraces. It took me half an hour to reach the bottom by foot. Once there, I found myself at the center of a frozen whirlpool of concentric rings. The sensation was disorienting and mildly hypnotic, and it was heightened by the strange acoustics. Bird calls echoed loudly, and I could hear the voices of people 50 feet away. These auditory effects have inspired theories that Moray could have been some kind of amphitheater. Though travelers and scholars have long noted the site's strange morphology, its function in Inca times is a source of enduring mystery.

Roger Atwood, a contributing editor to ARCHAEOLOGY, writes frequently on Latin American archaeology.